Wireless communication systems are not new. Indeed, two-way radio technology dates back to the beginning of the 20th century, while its progeny, cellular telephony systems, were first introduced in the early 70's. In traditional wireless communication systems, a wireless communication station facilitates wireless communication with remote communication device(s) (e.g., wireless subscriber units, mobile computing devices, and the like) via a wireless communication link(s). As the technology developed and the cost associated with owning and using such wireless communication devices has decreased, the popularity of the wireless telephony systems has exploded. To accommodate this growth in the subscriber base, digital cellular techniques were developed and standardized to increase user capacity of the cellular system without a commensurate increase in the radio frequency (RF) power generated within the system.
Initially, individual communication channels were defined as a carrier frequency, i.e., the so-called Frequency Division Multiple Access (FDMA) wireless systems. More recently, a number of different digital wireless communication technologies have been introduced and provide the basis for a number of wireless communication system architectures. Two primary examples of digital wireless technology are the time-division multiple access (TDMA) and code-division multiple access (CDMA) technologies.
In a TDMA system, a carrier frequency is parsed into independent incremental units of time, referred to as a timeslot, wherein each timeslot at a carrier frequency supports an independent communication session between a subscriber unit (or, handset) and a communication station (or, base station). That is, while a communication channel in a conventional analog (FDMA) communication system is commonly defined by its carrier frequency, a communication channel in a TDMA system is defined by a timeslot on a particular carrier frequency.
CDMA systems employ a broadband communication approach. In CDMA systems, a communication channel is defined by a pseudo-noise (PN) code contained in the header of digital communication packets passed between the subscriber unit and the communication station over rapidly varying signals throughout a spectrum of frequencies.
Those skilled in the art will appreciate that the wireless communication link between any two communicating entities is often the weakest portion of a communication chain, especially when the location of one or more of the entities is uncontrolled and moves. Under such circumstances, the radio link can become weak as the distance between the entities increases, or as obstacles occur in the physical path of the signal propagation. Furthermore, in the multiple access communication systems discussed above (e.g., FDMA, TDMA, CDMA, etc.) carrier frequency reuse is employed to support communication sessions among a number of geographically dispersed users. Such co-channel users are supposed to be separated geographically by sufficient distance so that their respective communication sessions do not interfere with one another. This constraint of geographic separation in frequency reuse limits the capacity of the system, and is often an imperfect guard against interference.
Adaptive array technology offers increased performance in such radio frequency (RF) networks by employing multiple antennae for radio transmission from one or more of the entities, controlling one or more of the relative phase and amplitude of the signal transmitted from each antenna within the array to spatially direct the RF energy towards desired recipients, and away from co-channel users.
This technique is very effective when the communication link is a point-to-point link, i.e., a wireless communication channel dedicated to communication between a single user terminal and a basestation, such as in conventional two-way communication systems. In an increasingly large number of wireless communication implementations, however, there is more than one intended recipient of a communication link, each of which should be able to receive the signal. An example of just such an implementation is the general packet radio service, or GPRS.
Those skilled in the art will appreciate that GPRS, as originally conceived, is implemented over a TDMA-based wireless communication system, wherein up to eight different users may selectively share a communication channel. From the end-user perspective, the GPRS service managed by a GPRS-enabled communication station provides a virtual packet-switched network utilizing circuit-switched communication resources of the TDMA system. Those skilled in the art will appreciate that a packet-based communication systems such as the GPRS facilitate the so-called “always on” connection to services via the communication link. In as much as conventional adaptive array techniques were derived in the context of a point-to-point communication link, it has been thought that two-way, multi-point, or “broadcast”, systems were not amenable to implementations of adaptive array technology.
Accordingly, a system and related methods enabling adaptive array technology within broadcast wireless communication systems is required, unencumbered by the limitations commonly associated with prior art broadcast systems. Just such a system and related methods are disclosed, below.